Secondary Menu

Big Dome Push Button & LinkIt Basics

Introduction: Big Dome Push Button & LinkIt Basics

When I first got Sparkfun's big dome push button in the mail, I was a little confused. Why were there 5 terminals on a button and no data sheet? Never fear! I've drawn up a quick guide. The two terminals on the side are for the LED. The terminal on the top (if you are holding the button upside down, as in the Illustration above) is the common. The two terminals sticking outwards are for push to make and push to break. You'll likely only need to choose one of those. Using the LED is totally optional and if you don't want your LED controlled by a microcontroller, you could also just hook up a battery to it if you want it on constantly.

Essentially, you need to connect one terminal to power and another terminal to a digital pin (I'm using 2). To the second terminal, you also want to connect through a pull down resistor to ground. See Illustration or try it out on 123d Circuits.

In this example, the only thing that happens is that "hello" is printed to the serial monitor followed by 1 if the button is pressed, and "0" if it isn't.

Simple code version:

int pushButton = 2;

// the setup routine runs once when you press reset:

void setup() {

// initialize serial communication at 9600 bits per second:

Serial.begin(9600);

// make the pushbutton's pin an input:

pinMode(pushButton, INPUT);

}

// the loop routine runs over and over again forever:

void loop() {

// read the input pin:

int buttonState = digitalRead(pushButton);

Serial.println("hello");

// print out the state of the button:

Serial.println(buttonState); // 1 is on (pushed), 0 is off

delay(10);

// delay in between reads for stability (1000 = 1 second).

}

Attachments

Step 1: Understanding State Changes

You'll notice that in the previous example, as long as the button is pressed, the serial monitor will display 1 repeatedly. And when the button is not pressed, the serial monitor will display 0 repeatedly. What if we are only interested in the state change--that is knowing when the button goes from unpressed to pressed and vice versa?

Attachments

Step 2: What's Next?

Now that we have a push button that can either detect when its state changes or constantly monitor its state, let's make something interesting that uses that information. Maybe it will be a travelling button that measures where and how often a big red button gets pressed. Maybe this button will be a dinner bell to tell everyone that food is ready. Maybe this big red button will do something else.